1. Field of Use
While the scotch yoke is subject to a wide range of applications, it is especially suited for use in a valve, such as a butterfly valve, and will be particularly described in that connection.
2. Description of the Prior Art
Scotch yokes have been used for many years in a wide variety of uses. They may be actuated either manually or automatically. When a load is placed on the input rod of the scotch yoke by an actuator, sideward thrust causes the input rod and yoke arm to bow and twist. This increases the friction on the sliding nut. At the extreme positions of travel of the sliding nut, the bowing and twisting become severe and the yoke arm tends to bind. This makes it difficult, if not impossible, to operate the scotch yoke manually. In addition, the plates of the yoke arm tend to separate and the yoke hub sometimes breaks.
In the past, it has been suggested to beef-up the yoke hub. This solution was satisfactory in the sense that it prevented the hub from breaking, but it did not eliminate the stresses which caused bowing and twisting. Therefore, manual operation of the yoke could still be extremely difficult.
It is an object of the present invention to provide a scotch yoke that is relatively inexpensive to manufacture.
It is a further object of the present invention to provide a scotch yoke that is relatively simple to manufacture.
It is a further object of the present invention to provide a scotch yoke that is very durable.
It is a further object of the present invention to provide a scotch yoke that is relatively easy to use.
It is a further object of the present invention to provide a scotch yoke having minimal sideward stress in the critical input members and minimal twisting stresses in the yoke assembly.
It is a further object of the present invention to provide a valve with a scotch yoke as mentioned herein.